Motor operated valves (commonly abbreviated as MOV on P&IDs) are valves which are actuated by electric motors. Motor operated valves are generally large valves used in different kinds of operations. Due to the large size of the valve actuator, an electric motor is needed to open or close a valve. Different types of motor operated valves are defined based on how those valves are actually opened or closed and what applications they are used for.
Types of motor operated valves are actually dependent on what kind of flow control can be achieved with these automated valves.
Motor operated valve types
Open / Close valves
These valves are simply used as on/off valves to turn the flow on or off. Precise flow control is not the primary intention here. Motors are used for opening and closing the heavy actuators of large valves. Some example applications include, pump discharge / suction valves, boiler feed water isolation valves, drum vent valves, product line valves etc.
These valves offer more precise flow control compared to the on/off valves. Motorized actuator facilitates gradual opening and closing of the valve enabling some degree of control over the flow. Some examples include, reflux lines, boiler start up vent, boiler IBD valves, boiler main steam valves etc.
Precision flow valves
Precision flow valves enable precise flow control, better than an inching valve. Motorized actuator in an inching valve operates in steps configured in the controller, e.g. 5%, 10% opening steps. Hence flow control can also be done in brackets of 5-10% with that much margin for error.
On the other hand, in case of precision flow valves, continuous flow control is enabled by the use of proper feedback from the field to the controller which is not usually found in other motor operated valves. An example is steam injection valve / water injection valves used in GT for Nox control.
Different type of valves with motorized actuators
Types of motorized valves discussed above is based on the flow control capabilities. But that aside, different types of valves, can also be used as motor operated valves by simply using a motorized actuator for any valve.
Some examples of different types of motorized valves -
Motor operated gate valve
Motor operated butterfly valve
Motor operated ball valve